The contractors who helped build the new health care website are not to blame for the problems that countless users have encountered at HealthCare.gov, company representatives told the House Energy and Commerce Committee today.

Cheryl Campbell, who testified on behalf of CGI Federal, the key contractor behind the construction of HealthCare.Gov, conceded that issues arising in the federal exchange "made the enrollment process difficult for too many Americans." But she directed blame at the federal Centers for Medicare and Medicaid Services, which integrated the work of multiple contractors as the final product was launched.

The Centers for Medicare and Medicaid Services is part of the U.S. Department of Health and Human Services.

"From a CGI perspective, our portion of the application worked as designed. People have been able to enroll, not at the pace, not as the experience we would have liked," Campbell, a senior vice president at CGI Federal, said. "But the end-to-end testing was the responsibility of CMS."

CGI is a subsidiary of CGI Group, a Montreal-based conglomerate.

While Campbell, who said she is responsible for all CGI Federal projects at the Department of Health and Human Services, largely deflected singular culpability for the website's problems, both Republicans and Democrats on the committee pressed the contractors for a credible explanation of the botched start.

Andrew Slavitt, the group executive vice president for Optum/QSSI, whose contract was responsible for building a data services hub for President Obama's health care law, said the site was "inundated by many more consumers than anticipated," but the bugs were prioritized as they were identified after the launch.

"Many of the critical components developed by these multiple vendors were overwhelmed, including the virtual data center environment, the software, the database system and the hardware, and our [Enterprise Identity Management] tool," Slavitt testified. "We understand the frustration many people have felt since healthcare.gov was launched. We have been and remain accountable for the performance of our tools and our work product."

Rep. Anna Eshoo, D-Calif., said, "There are thousands of websites that carry far more traffic. So I think that's really kind of a lame excuse. Amazon and eBay don't crash the week before Christmas and ProFlowers doesn't crash on Valentine's Day.

"Are you saying that you didn't test? That the test worked very well, both inside and out? Or that you turned it all over to CMS? Anybody want to answer?" Eshoo continued, drawing a long period of silence from all of the witnesses. "If you don't have an answer, just say that you don't."

Given the $500 million cost of the website, committee chairman Fred Upton said Americans "really expected a user-friendly program, system," but the website was not ready to go live.

"Over the last several months leading up to the October 1st launch, top administration officials and lead contractors appeared before this committee, looked us in the eye and assured us repeatedly that everything was on track. Except that it wasn't, as we all know too well," Upton, R-Mich., said. "Whether it's like ordering a pizza, an airline flight, a rental car, a hotel, it's a standard that many were expecting to see, and I think most at this point would say it's really not ready for prime time."

Rep. Tim Murphy, R-Pa., agreed. "After footing the bill, the American people deserve something that works or start over," he said. "Take responsibility, tell us what's wrong, fix it or try something else."

The witnesses had previously testified at the committee leading into the website's launch, and had expressed confidence that the website's performance would meet expectations.

"If there was a silver bullet answer to that question, I'd give it to you," Campbell answered. "It is a combination of a number of things. It is not just a component of what CGI's responsible for. It's the end-to-end aspect that is the challenge."

"Why were we told everything was OK a few weeks before one of the biggest IT disasters in government history," Pitts asked.

"We were not part of the end-to-end visibility throughout the system to understand exactly what [would happen]," Campbell replied.

Rep. Joe Barton, R-Texas, asked Campbell whether the site is "a system that you're proud of?"

"This is a system that we are working every day to make improvement," Campbell responded.

"If we have a system that almost no one can successfully navigate, that we have to go to the paper system of this gentleman's company down here, that is a system that has failed," Barton shot back.

Other members of the committee questioned whether the problems will be fixed before Jan. 1, when people who haven't signed up would face a fine.

"CMS has had three years and most of you have had over a year to ensure that this law could work," Rep. Ralph Hall, R-Texas, said. "What do you want me to tell the Americans who are terrified of really facing IRS fines for not being able to access coverage they actually can't afford?"

"I would tell your constituents that the system is improving day over day and that we're continuing to work to make improvements for them to be able to enroll," Campbell told Hall.

"I'm asking for help. I want help," Hall, the oldest member of Congress at age 90, said. "I have 700,000 people that I have to report to, and I think about 690,000 of them hate the Obama law."

Campbell later testified that while "there's improvements day over day," she "cannot give you an exact date as to when it will be completely to satisfaction."

The hearing lasted more than four hours. HHS Secretary Kathleen Sebelius is expected to testify before the same committee Wednesday.